This section provides background information related to the present disclosure which is not necessarily prior art.
In normal operations electronic/electric devices in installations usually generate undesirable electromagnetic energy, and such electromagnetic energy interferes with the operation of adjacent electronic/electric devices due to electromagnetic interference (EMI) transmissions generated via radiation. Such radiation results in electromagnetic interference (EMI) or radio frequency interference (RFI), which can interfere with the operation of other electronic devices within a certain proximity. Without adequate shielding, EMI/RFI may cause degradation or complete loss of important signals, thereby rendering the electronic equipment inefficient or inoperable. A common solution to ameliorate the effects of EMI/RFI is through the use of shields capable of absorbing and/or reflecting EMI energy. These shields are typically employed to localize EMI/RFI within its source, and to insulate other devices proximal to the EMI/RFI source.
A conventionally common shielding technique includes an apparatus or structure consisting of two component parts, namely a framework and a lid where the lid is mounted onto the framework. This shielding apparatus is functional to shield electric or electronic devices or components covered by the framework and the lid when the framework is mounted onto a PCB (printed circuit board) via a surface mount technology (SMT) welding method and then electrically connecting and mounting the lid onto the framework.
With such a two-part EMI shielding apparatus, the two component parts may have spacing between adjacent portions of the lid and the framework. This spacing allows EMI to pass therethrough, thereby reducing the shielding effectiveness of the two-part EMI shielding apparatus. With the tendency towards higher frequencies generated by more and more electronic devices, it is desirable, in order to acquire the desired shielding effect and to avoid RF (radio frequency) leak from the spacing, to reduce the spacing between the lid and the framework to be as small as practically possible.
To mount the lid onto the framework with currently available two-component shielding apparatus, bayonet catches or projections may be provided on the lateral sides of the lid and the framework. Since the bayonet catches or projections are located at the lateral side of the lid and the corresponding lateral side of the framework, it is necessary after assembly of the lid with the framework for the lateral side of the lid to partially overlap with the lateral side of the framework so that the bayonet catches or projections engage. But it is difficult to guarantee good engagement at each engaging location, and inferior engagement appears at locations of certain bayonet catches or projections, thus possibly increasing the fitting clearance. Resultantly, it is very difficult to achieve zero fitting clearance at the conjunction between the assembled lid and framework, and presence of such fitting clearance undermines the grounding and shielding performance and might lead to RF leak.
The term “EMI” as used herein should be considered to generally include and refer to EMI emissions and RFI emissions, and the term “electromagnetic” should be considered to generally include and refer to electromagnetic and radio frequency from external sources and internal sources. Accordingly, the term shielding (as used herein) generally includes and refers to EMI shielding and RFI shielding, for example, to prevent (or at least reduce) ingress and egress of EMI and RFI relative to wiring, cabling, or an enclosure in which electronic equipment is disposed.